1. Field of the Invention
This invention relates to an improvement of a rear suspension system for motorcycles which is provided with a progressive linkage mechanism wherein a compression stroke of the damper for the rear wheel suspension is progressively increased against the oscillating stroke of a rear wheel supporting member.
2. Description of Relevant Art
It is well known in the art to provide a rear suspension system for motorcycles in which a rear wheel supporting member having its rear end supporting the rear wheel and its front end pivotally connected to the chassis frame, in such a manner that it may be oscillated in an upward or downward direction, absorbs and dampens the vertical oscillation caused by the rear wheel which is oscillated around the front wheel due to an uneven road surface. The damper has one end connected to the chassis frame and is connected to the rear wheel supporting member at the other end thereof by a first link, and the chassis frame is connected to the first link by a second link, whereby a progressive linkage mechanism including the first and second links is installed between the damper and the rear wheel supporting member. In such a rear suspension system as constructed by the progressive linkage mechanism, when the rear wheel supporting member is oscillated in an upward direction, the first link is rotated around the connecting part with the rear wheel supporting member by the second link while it is moved upwardly along with the rear wheel supporting member, and the damper is compressed by the first link. As a result, a compression stroke of the damper is progressively increased in a curve of secondary degree with respect to the oscillating stroke of the rear wheel supporting member and thus the characteristic of the dampening force may show a progressive performance.
Such a conventional type of rear suspension system as described above has been installed mainly in a motorcycle manufactured for off-road use on an uneven road surface, and if this system is applied to a motorcycle to be driven primarily on an even surface road, it is not preferable to install the conventional progressive linkage mechanism in the motorcycle in its unmodified form. That is, in a general type of on road motorcycle, a battery with a relatively large capacity and other bulky equipment such as an air cleaner are assembled in the chassis frame, so that it is preferable to assemble the progressive linkage mechanism in a small space in relation to these units requiring a large installation space and to make a compact sized construction to permit storing of the mechanism. Further, when a degree of rotation of the first link which is rotated while it is moved upwardly is relatively high, it is required to keep a space for allowing the first link to be moved, and as a result sizes of the units are substantially restricted.
The present invention effectively overcomes the above-mentioned disadvantages in applying the progressive link type rear suspension system to motorcycles for on-road use.